Electric-field control of magnetoresistance
Final Report Abstract
Pulsed laser deposition was used to grow thin ZnCoO layers on c-plane sapphire substrates with a Co concentration of 5 at. %. The ZnCoO films have a charge carrier concentration below the metal-insulator transition and reveal a large positive magnetoresistance at low temperatures due to s-d exchange interaction. Temperature and magnetic field dependent diode currents have been measured between a rectifying Au/AgxO contact and a nonrectifying Au/Ti contact in top-top configuration. At low temperatures the ZnCoO films are completely depleted below the Au/AgxO Schottky contact and the diode current can be persistently reduced in an external magnetic field. Bound magnetic polarons can be parallel aligned in an external magnetic field, percolate, and may reveal a huge internal magnetic field. Free charge carriers which are pulled through percolating bound magnetic polarons are experiencing an increased path length due to Lorentz forces. Therefore, the charge carrier mobility is decreased in the depleted regions of ZnCoO. This effect is persistent at low temperatures and reversible only if the ZnCoO is heated above 300 K. Such a huge magnetoresistance can be possibly observed also in other depleted magnetic semiconductors and can be used to switch the transport properties in circuitry with integrated magnetic semiconductors, e.g. optical isolators, magnetic sensors, and non-volatile memories, between two resistance states and to spinpolarize free charge carriers. We expect that such spintronics devices are another step towards low energy consuming information processing technologies.
Publications
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3d transition metal diffusion in diluted magnetic semiconductors prepared by pulsed laser processing. subtherm 2011, 25.- 27.10.2011, Dresden, Germany
Bürger, D.; Seeger, M.; Zhou, S.; Skorupa, W. & Schmidt, H.
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Transparent field effect transistor with spin-polarized electrons. DPG Spring Meeting of the Condensed Matter Division, Dresden, 13.-18.03.2011, Germany
Kaspar, T.; Bürger, D.; Skorupa, I.; Kühn, V.; Erbe, A.; Helm, M. & Schmidt, H.
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Field effect transistors with s-d spin-polarized electrons in the magnetic channel. DPG Spring Meeting of the Condensed Matter Division, Berlin, Germany, 25.-30.03. 2012
Kaspar, T.; Bürger, D.; Skorupa, I.; Kühn, V.; Erbe, A.; Helm, M. & Schmidt, H.
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Transition metal diffusion in diluted magnetic Si and GaAs prepared by pulsed laser processing. J. Appl. Phys. 111 (2012) 054914
Bürger, Danilo; Seeger, Michael; Zhou, Shengqiang; Skorupa, Wolfgang & Schmidt, Heidemarie
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Persistent Current Reduction in Metal-Semiconductor FETs With a ZnCoO Channel in an External Magnetic Field. IEEE Elect. Dev. Lett. 34 (2013) 1271
Kaspar, Tim; Fiedler, Jan; Skorupa, Ilona; Burger, Danilo; Mucklich, Arndt; Fritzsche, Monika; Schmidt, Oliver G. & Schmidt, Heidemarie
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Metall-Halbleiter-Feld-Effekt-Transistoren mit magnetischem Halbleiterkanal auf Zinkoxidbasis. Dissertation, Technische Universität Dresden, 2014
Kaspar, T.
